Technical Field
The invention relates to a vibration-limiting module. The invention additionally relates to a device having such a vibration-limiting module, to a structural segment for a structural installation having such a vibration-limiting module, and to a wind turbine having a tower and a tower segment having such a vibration-limiting module.
Description of the Related Art
A wind turbine constitutes a structure that is particularly susceptible to vibration, because of the height and slenderness of its structural form; this applies particularly to tubular steel and prestressed concrete wind turbine towers, which are increasingly being designed for greater rotor hub heights, thereby increasing susceptibility to unwanted vibration. In particular, resonance phenomena of a rotating rotor, which might have vibrating rotor blades, may result in a wind turbine having complex modes, particularly also on the tower of the wind turbine. Nevertheless, it is increasingly important for the wind turbine tower to be constructed in a manner that is sparing of resources, e.g., in respect of reduction of the diameter and wall thickness of the tower. This applies, in principle, to any type of structural form of a wind turbine, but particularly to a wind turbine that has a tubular tower such as, for example, a tubular steel tower or a precast concrete tower.
A wind turbine of known structural form comprises a nacelle, which is mounted on a tower and carries a rotor. Known in the art is the practice of mounting a vibration absorber in the tower. For example, EP 1 008 747 B1 describes a vibration absorber for damping vibrations in a wind turbine by means of an inertia mass, a pendulum rod, a pendulum bearing, or pendulum joint, and damping means. The absorption property is achieved in that the inertia mass vibrates with a phase displacement relative to the structure of the wind turbine. The damping means constitute a structural unit with the pendulum joint, and including one or more elastomer modules, the absorber being such that it can be accelerated in any direction of a plane.
Basically, a vibration absorber is to be understood to mean a structural module that includes a mass and at least one spring and that, as a result of being connected to a vibratory system such as, for example, a wind turbine, can reduce vibrations of that system. The vibration-absorber mass, also referred to as a counter-oscillatory mass, vibrates, in particular, with a phase displacement relative to the main structure of the structural installation such as, for example, a wind turbine. The forces of the vibration absorber that result from acceleration can be passed into the main structure of a wind turbine in which vibrations are to be abated. The effect of a vibration absorber is not limited merely to the point of application of the absorption excitation, but is also effective for other points on the connected main structure. Basically, a vibration absorber can be used for a relatively narrowly limited vibration disturbance frequency, since the vibration absorber generally provides a vibration absorption frequency that is variable only to a limited extent; a vibration absorber is thus to be regarded rather as a static component for reducing vibration. An essential advantage of a vibration absorber, however, consists in that it is comparatively well matched to the unwanted vibration to be absorbed and, if appropriately designed, can almost completely cancel out this unwanted vibration. It must be taken into account that, in the case of absorption there is to be observed, for the coupled system constituted by the vibration absorber and the main structure capable of unwanted vibration, e.g., the wind turbine, a frequency splitting that is outside the absorber frequency, or outside the original vibration disturbance frequency, and that might result in greater vibration amplitudes outside of the absorber frequency.
In contrast to the vibration absorber, a vibration damper, although it can be used in supplement to the vibration absorber, is to be regarded as a system that, by means of a spring and a damper element, connects the counter-oscillatory mass to the main structure that is to be damped. The spring elements and damper elements in this case may be of various designs. Vibration dampers are basically considered to be dynamically acting systems and, compared with a pure vibration absorber, can be used for a broader spectrum of differing disturbance frequencies.
To that extent, the structure of a vibration absorber designated in EP 1 008 747 B1 may be designated rather as a vibration damper. The system, as such, may be designated as a passively acting system.
Concepts for reducing vibration by passive action use damped or undamped structures, which have a mechanically functioning spring and mass system, on a main structure that exhibits unwanted vibration. The use of a passive vibration absorber is particularly suitable for the case, for example, in which the frequency of an unwanted vibration is comparatively well known and lies within a comparatively closely delimited and known frequency range. Irrespective of this, a passive system can be expanded through the provision of an active control element, and thus developed to form an active system; this is effected, for example, in that significant parameters of a main structure or, in particular, of the vibration absorber or vibration damper, are adjusted in real time to variable conditions of the main structure. As a result, other disturbance frequencies that are close to a primarily resonant frequency of a main disturbance frequency can be absorbed and/or damped over a comparatively broad band. In most cases, however, this approach requires an elaborate feedback control system and an external energy supply.
A vibration absorber system, which has a variable natural frequency of the absorber and which can be set in a variable but fixed manner to differing disturbance frequencies, is known from DE 20 2005 019 949 U1. In the latter, an absorber system, realized as an upright pendulum and having an absorber mass, is supported on a base via a spring arrangement, and a basic distance of the center of gravity of the absorber mass can be varied. Provided parallel to the spring arrangement, between the absorber mass and the base, there is a distance definition element, which is resistant to compression and/or tension and variable in length. Basically, such or other upright absorber devices can preferably be used for damping in buildings. DE 197 34 993 A1 describes a comparatively complex reduction of vibration in the case of a building, based on an upright pendulum.
In order to protect structural installations that are susceptible to vibration, it is desirable to provide a vibration limitation system that is comparatively effective in operation, in particular by means of appropriate reduction in the amplitude of an unwanted mode, in particular primarily by means of vibration absorption, that is nonetheless of a reliable design and, moreover, can be constructed in a comparatively simple manner and/or made available in a manner permitting its manipulation.
In the priority application relating to the present application, the German Patent and Trademark Office has researched the following prior art: DE 20 2005 019 949 U1, U.S. Pat. No. 6,672,763 B1, EP 1 008 747 B1 and DE 197 34 993 A1.